**Exhibit 99.1**

 

**AMENDEDFORM 51-101F2REPORT ON RESERVES DATA BYINTERNAL QUALIFIED RESERVES EVALUATOR**

To the Board of Directors of Nexen Inc. (the “Company”):

1.                                       Companystaff and I have evaluated the Company’s reserves data as at December 31, 2006.The reserves data consist of the following:

(a)                                  provedoil and gas reserve quantities estimated as at last day of the Company’s  most recently completed financial year usingconstant prices and costs; and

(b)                                 therelated standardized measure.

(both (a) and (b) formpart of the “FAS 69 Disclosures about Oil and Gas Producing Activities”contained in the Company’s Supplementary Financial Information in its Annual Reporton Form 10-K).

2.                                       Thereserves data have been prepared in accordance with:

(a)                                  UnitedStates’ Securities and Exchange Commission (SEC) requirements;

(b)                                 generallyaccepted industry practices in the United States; and

(c)                                  thestandards of the Canadian Oil and Gas Evaluation Handbook modified to the extentnecessary to reflect SEC requirements.

(collectively, the NexenReserves Standards).

3.                                       Thereserves data are the responsibility of the Company’s management. Myresponsibility is to express an opinion whether the evaluation was carried outin accordance with the Nexen Reserves Standards.

4.                                       Iam not independent of the Company, within the meaning of the term “independent”under National Instrument 51-101.

5.                                       Amongother things, with respect to matters regarding royalties, operating costs,development plans and costs, abandonment plans and costs, and income taxes(where applicable), I have placed reasonable reliance on the information anddecisions of others in their areas of authority, responsibility and expertisewithin the Company.

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6.                                       Inmy opinion, the reserves data has, in all material respects, been prepared inaccordance with the Nexen Reserves Standards.

7.                                       Reservesare estimates only and not exact quantities. Estimates of economicallyrecoverable oil and natural gas reserves and future net cash flows are based ona number of variable factors, assumptions and judgements regarding futureevents. It is believed that the factors and assumptions used and judgementsmade in estimating reserves are reasonable based on the information availableat the time the estimates were prepared. Actual results will vary and such variances could be material.

8.                                       Ihave no responsibility to update this opinion for events and circumstancesoccurring after the date of this opinion.

9.                                       Ihave signed this Form F2 in my capacity as an employee of Nexen Inc. and not inmy personal capacity.

 
| **/s/ Ian McDonald**                       | ** ** |
|--------------------------------------------|------------|
| **Ian McDonald**                           | ** ** |
| **Nexen  Inc.**                            | ** ** |
| **Internal  Qualified Reserves Evaluator** |
| **Calgary,  Alberta**                      | ** ** |
| ** **                                 | ** ** |
| **February  14, 2007**                     | ** ** |

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